#include <bits/stdc++.h>
using namespace std;
using uint=unsigned int;
using ll=long long;
using ull=unsigned long long;
using i128=__int128;
const int N=1e6+5;

void solve(){
    int n,m,k;
    cin>>n>>m>>k;
    vector<int> a(n);
    for(int i=0;i<n;i++){
        int val;
        cin>>val;
        a[i]=abs(val-k);
    }
    sort(a.begin(), a.end());
    cout<<a[m-1]<<endl;
}

int main(){
    ios::sync_with_stdio(false);
    cin.tie(nullptr);
    cout.tie(nullptr);
    solve();

    return 0;
}